WO2020021432A1

WO2020021432A1 - Painting plant with overspray removal system, removal method and device

Info

Publication number: WO2020021432A1
Application number: PCT/IB2019/056244
Authority: WO
Inventors: Paolo COLOMBAROLI; Diego Molteni
Original assignee: Geico Spa
Priority date: 2018-07-23
Filing date: 2019-07-22
Publication date: 2020-01-30
Also published as: IT201800007446A1; EP3826773A1; BR112021000488A2; CN112423898B; CN112423898A

Abstract

A liquid-paint painting plant (10), comprising a painting booth (11) inside which the liquid paint is sprayed and devices for extracting an air flow from the booth (11) towards a filtering unit (17) for the removal of overspray particles from the air flow. The plant also comprises microwave means (22) which treat the air flow extracted from the booth (11). This ensures effective elimination of the overspray. A removal method and device are also described.

Description

Title

“Painting plant with overspray removal system, removal method and device"

Description

The present invention relates to a painting plant provided with an innovative system for removal of the overspray. The invention also relates to a method and a device for removal of the overspray.

In spray-painting technology the problem of so-called "overspray" - i.e. excess particles of paint which are not deposited on the object to be painted and which must therefore be removed from the painting booth - is well-known. The removal of the overspray is usually performed by means of a suitable air flow which crosses the booth.

The air flow evacuated from the booth is therefore contaminated with the particles of paint and must be purified before it can be released into the environment or introduced back into the booth.

For this purpose, various removal systems, for example of the electrostatic type or with integrated filters suitable for filtering the liquid particles, have been proposed. These systems are generally complex and require a high degree of maintenance owing to the highly adhesive nature of the paint.

Systems for eliminating the overspray are known where a stream of continuously recirculating water is used to capture the particles of paint present in the air flow.

The water, which in turn has been contaminated by the particles of paint, must be purified before it can be introduced again into the paint booth, or else disposed of.

This overspray removal system, although widely used, is not without drawbacks since it requires specialized labour for the water purification operations; furthermore, the management of a booth with recirculation of the air, where the air passes through a stream of water and therefore undergoes a change in its temperature and moisture conditions, is particularly costly from an energy point of view, since the air must be reconditioned before it can be introduced into the booth again.

Systems for eliminating the overspray by means of powder inertization have also been proposed where the air flow is conveyed through a filtering system composed of a chamber inside which a suitable powder inerting product (for example calcium carbonate) is blown, said powder absorbing the particles of paint and being then intercepted by normal powder filters.

This system has the advantage that it does not modify the temperature and moisture conditions of the air and therefore makes recirculation of the air inside the booth more cost-effective.

This system requires, however, a relatively large quantity of powder which must then be disposed of, resulting in high disposal costs. Also the procurement of the powders is not always easy and may involve further costs.

Moreover, relatively complex techniques are required in order to move the large quantity of powder, blow it in a uniform manner into the chamber, intercept it and evacuate it efficiently from the air flow after absorption of the paint.

The filters themselves are costly and require relatively frequent maintenance in order to prevent them from becoming completely blocked up.

Moreover, the substantially random distribution of the powder inside the chamber may not be sufficient to completely neutralize the overspray and prevent the paint from adhering to the walls of the chamber.

Other overspray removal systems are also known where the air flow is forced to follow a path with sudden changes in direction such that the particles of paint (which, being heavier, tend not to change direction) end up striking paper filters which they encounter along their path, adhering to them.

However, a large number of filters arranged in succession are needed in order to eliminate all the particles of paint present in the air flow. Furthermore, this system requires continuous monitoring of the state of the filters, maintenance and disposal thereof, these being costly operations.

The general object of the present invention is to provide a painting booth with an overspray removal system and an overspray removal method which are able to overcome the drawbacks mentioned above with reference to the prior art.

Another object of the present invention is to achieve the effective elimination of the overspray (or particles of paint).

Further objects are those of ensuring less maintenance, lower management and operating costs and finally fewer disposal problems, compared to the known systems.

In view of these objects the idea according to the invention is to provide a liquid-paint painting plant as claimed in claim 1 and a device for removal of liquid paint overspray from an air flow as claimed in claim 15.

Another idea of the invention is to provide a method for removal of the overspray in the air flow exiting from a booth in a liquid paint spray-painting plant, as claimed in claim 10

In order to illustrate more clearly the innovative principles of the present invention and its advantages compared to the prior art, examples of embodiment applying these principles will be described below with the aid of the accompanying drawings. In the drawings:

- Figure 1 shows a schematic front view of a first embodiment of a painting booth applying the principles of the invention;

- Figure 2 shows a schematic front view of a second embodiment of a painting booth applying the principles of the invention;

- Figure 3 shows a schematic front view of a third embodiment of a painting booth applying the principles of the invention.

With reference to the figures, Figure 1 shows a first embodiment of a painting plant according to the invention, denoted generally by 10.

The plant 10 comprises a painting booth 1 1 for painting objects 12 (for example motor vehicle bodies). The objects 12 to be painted are advantageously transported into the painting booth 11 by means of a known conveyor belt 13, for example an intermittent or continuous conveying line.

The booth 11 contains automatic or manual painting devices 14 which, when activated, spray liquid paint onto the surfaces of the object to be painted. Advantageously, the painting devices 14 may be realized in the form of known robot arms provided with spray guns or cups at their ends.

An air flow is made to pass through the booth 1 1 in order to remove from it the overspray by means of air flow extraction devices (for example indicated by 18 in the figures). These devices (for example comprising fans or suction units) may be realized in various ways, as may be per se easily imagined by the person skilled in the art.

Advantageously, extraction is performed through a floor 15 of the booth 1 1 composed of grates through which the air in the booth is drawn so as to evacuate the overspray from the booth.

The ceiling of the booth 1 1 therefore has advantageously formed therein corresponding air inlets 16 which are also advantageously provided with grates and filters so as to have a continuous air flow which passes vertically through the booth from the top downwards during the painting operations.

The air flow exiting the booth 1 1 contains overspray in the form of excess particles of paint and is conveyed to a removal device which may comprise a filtering unit 17.

Suitable suction units or fans 18, present along the air flow path, may form or be included in the extraction devices in order to move suitably the air flow towards the filtering unit 17 from where the cleaned air exits and is evacuated externally by means of a duct 19 and/or conveyed back to the ceiling of the chamber vis the duct 20.

An air supply system 21 , which may have associated known conditioning systems, is provided with the possibility of recirculating or entirely renewing the air.

The plant according to the invention comprises a device for removal of the overspray which also uses microwaves.

In particular, along the conveying path between the booth 1 1 and the filtering unit 17, the air flow is subjected to the action of microwave means 22, so as to at least reduce the adhesive nature of the particles.

In particular, the preferred microwave means 22 comprise at least one microwave emitter 221 able to irradiate the air flow suitably and for a certain exposure time period sufficient to dry at least partly the particles of overspray.

Advantageously, the time period for exposure of the air flow comprising the particles of overspray for the purposes of the present invention may vary between 0.5 and 4 seconds. Microwave generators or emitters are per se well-known by the person skilled in the art and therefore will not be further described or shown here.

The at least one microwave emitter 221 may be chosen from among known microwave production devices, such as solid-state devices or vacuum tubes.

The at least one microwave emitter 221 is preferably chosen so as to emit an electromagnetic radiation in a range of 2450 MHz +/- 50 MHz

The emission power of the microwave emitter 221 will also depend on the amount of air to be treated per unit of time. Advantageously, for the purposes of the invention, the at least one microwave emitter 221 may emit electromagnetic waves with an intensity of between 2 and 5 mW/cm². Advantageously, the plant 10 may also be provided with a plurality of microwave emitters 221 arranged in succession along the path for conveying the air flow from the booth 1 1 to the filtering unit 17. For example, as may be seen in Figure 1, a plurality of emitters 221 may be arranged along a vertical section of the plant 10 downstream of the painting booth 11, for example inside a chamber 24 for conveying the air flow from the floor of the painting booth 11 to a duct 26 leading to the filtering unit 17.

The plant 10 may also be provided with a plurality of microwave emitters 221 arranged in parallel transversely with respect to the path for conveying the air flow from the floor 15 to the filtering unit 17. For example, as can be seen in Figures 1 and 2, microwave emitters 221 may be provided on both sides of the air flow and/or spaced from each other so as to irradiate better the air flow.

According to the principles of the invention, all the air flow carrying the overspray may be irradiated by microwaves and, consequently, the particles of paint may be dried at least superficially before they touch and adhere inside the plant 10 (for example, to the walls of the conveying chamber 24) while they are conveyed towards filtering unit 17.

The filtering unit 17, in accordance with the present invention, must therefore treat an air flow which has, dispersed therein, particles of paint that are no longer adhesive or are less adhesive.

The filtering unit 17 may, for example, comprise one or more conventional solid particle filters 171 (depending on the degree of filtration required) such as bag, cartridge, plate or rigid-membrane filters, depending on the separation efficiency required by the system. According to a preferred configuration, as shown in Figure 1 , the filtering unit 17 has 171 filters which are crossed by the air flow in a vertical direction. A hopper 172 may therefore be advantageously positioned below said filters 171 so that the dried particles of paint fall through the hopper 172 into a storage vessel 23.

Cleaning of the filters with a counter-flow of compressed air may be carried out cyclically in order to facilitate falling of the particles intercepted by the filters 171.

If the overspray particles are still partially adhesive after the microwave treatment, a powder overspray removal system may again be used, for example by introducing powder into the air flow reaching filtering unit 17.

Owing to the reduced adhesion of the microwave-treated overspray, the use of powder will in any case be limited compared to the prior art.

According to the principles of the invention, the air flow must in any case be separated from a smaller number of particles and, therefore, the amount of waste product of plant 10 is smaller. Advantageously, also, said waste product may be directly reused in other applications (for example, as a filler material).

Various conveying systems may be set up to convey the air flow contaminated with particles of paint from the booth 11 to the filtering unit 17.

This conveying system may comprise, for example, at least one conveyor 25 connecting the area underneath the grating floor 15 and a discharge duct 26 connected to the air flow filtering unit 17.

Advantageously, the at least one conveyor 25 has the form of an inverted pyramid.

Moreover, the internal walls of the at least one conveyor 25 may be coated with known anti-adhesive materials.

For example, as shown in Figure 1, the plant 10 may be provided with a single conveyor 25 covering the whole of the grating floor 15 of the painting booth 11.

Figure 2, on the other hand, shows an alternative embodiment with a plurality of conveyors 25 underneath the grating floor 15. For the sake of clarity, similar elements in the various embodiments will be indicated by the same numbering.

Advantageously, at least one microwave emitter 221 is arranged in the region of at least one conveyor 25.

The plant 10 may also be equipped with a shield for electromagnetic waves (Faraday cage), not shown in the figures, to prevent microwaves escaping from the said plant. Advantageously, the at least one microwave emitter 221 is suitably shielded with a Faraday cage.

As shown in broken lines in Figure 1, the emitter 221 may also be placed along a narrow section or duct for conveying the air flow to the filtering unit 17, or even directly inside the filtering device 17 itself.

Figure 3 shows a further possible variant of a plant 10 according to the invention. In this variant the air flow with overspray which crosses the grating floor 15 from the painting booth 11 is directed into the conveying chamber 24 where conveyor partitions 25 guide it across the microwave means 22. These microwave means 22 comprise a chamber 223 which is advantageously incorporated in the chamber underneath the painting booth 1 1 and inside which the microwaves act by means of microwave generators 221. The generators 221 are advantageously placed on opposite side walls of the chamber so to strike the air flow with microwaves transversely with respect to the air flow.

The chamber 223 has an inlet and outlet for the air flow with overspray advantageously on opposite sides of the chamber. These opposite sides are advantageously delimited by screens 224, 225 of a type known per se (e.g. suitable metal grates) which allow the overspray air to pass through, but prevent microwaves of dangerous intensity from escaping.

After crossing the chamber 223, the air flow with overspray dried at least partially by the microwaves is conveyed to the duct 26 so as to reach the filtering unit 17. The remaining components of the plant may be similar to those already described above. The structure in Figure 3 is particularly compact and efficient.

At this point it is clear how the predefined objects are achieved.

The plant obtained according to the present invention allows the implementation of an effective method for removal of the overspray while limiting the complexity of the removal system.

The system according to the invention results in a plant with a reduced number of machine stoppages for maintenance.

In addition, the cleaning operations required are also reduced since the particles of overspray after the microwave treatment are less likely to adhere inside the plant. This also results in a better state of wear over time of the plant components, such as the conveyors, which therefore do not have to be cleaned with abrasive products.

The waste product will be dry and consist of a minimum quantity and may also be recycled, thus constituting an added value rather than a disposal cost.

Obviously the above description of an embodiment applying the innovative principles of the present invention is given by way of example of such innovative principles and must therefore not be regarded as limiting the scope of the rights claimed here.

For example, the conveyor may be in direct communication with the filtering unit or additional connection systems may be provided.

The device for removal of the liquid paint overspray from an air flow according to the invention, using at least one microwave emitter and a possible following filtering device, may of course be incorporated in a painting plant different from that illustrated here by way of example.

Claims

1. Liquid-paint painting plant (10), comprising:

- a painting booth (1 1) inside which the liquid paint is sprayed;

- a filtering unit (17);

- devices (18) for extracting an air flow from the booth (1 1) towards the filtering unit (17) for the removal of overspray from the air flow,

characterized in that it comprises microwave means (22) which treat the air flow extracted from the booth (1 1).

2. Plant (10) according to claim 1, characterized in that the microwave means (22) comprise at least one microwave emitter (221).

3. Plant (10) according to claim 2, characterized in that the microwave means (22) comprise microwave emitters (221) arranged in succession along a path for conveying the air flow from the booth (11) to the filtering unit (17).

4. Plant (10) according to claim 2 or 3, characterized in that the microwave means (22) comprise microwave emitters (221 ) arranged in parallel transversely with respect to the path for conveying the flow from the booth (11) to the filtering unit (17).

5. Plant (10) according to any one of claims 2-4, characterized in that the microwave means (22) emit electromagnetic radiation in a range of 2450 MHz +/- 50 MHz.

6. Plant (10) according to any one of claims 2-5, characterized in that the microwave means (22) emit electromagnetic radiation with an intensity of between 2 and 5 mW/cm².

7. Plant (10) according to any one of claims 2-6, characterized in that it is provided with a shield designed to prevent the microwaves from escaping.

8. Plant (10) according to any one of the preceding claims, characterized in that the booth (1 1) comprises a grating floor (15) for exit of the air flow towards the filtering unit (17) and at least one conveyor (25) with inlet arranged near and below the grating floor (15).

9. Plant (10) according to claim 8, characterized in that the microwave means (22) are positioned in the region of the at least one conveyor (25).

10. Method for removal of the overspray in the air flow exiting from a booth in a liquid paint spray-painting plant, comprising the steps of:

- treating the air flow with microwaves; and

- subsequently filtering the air flow with a unit (17) for filtering the overspray in the air flow.

11. Method according to claim 10, characterized in that the microwave frequency is in a range of 2450 MHz +/- 50 MHz.

12. Method according to claim 10, characterized in that the intensity of the microwaves is between 2 and 5 mW/cm .

13. Method according to claim 10, characterized in that after the microwave treatment the air flow passes through a powder system for removal of the overspray.

14. Method according to claim 10, characterized in that the microwave treatment is performed until at least superficial drying of particles of the overspray occurs.

15. Device (17,22) for removal of the liquid paint overspray from an air flow, characterized in that it comprises an overspray air flow path along which at least one microwave emitter (221 ) for at least partial drying of the overspray is present, and a filtering unit (17) for the filtering of the overspray.